For membership-oriented websites, registration forms are one of the most important parts. A problematic experience, even if the sign-up is completed, will place a "question mark" to the visitor or vice-versa.

And, it is also the first step where you can show that you care about the security of the website & all the data collected.

Although you can control/improve the security of the website, it is sometimes the weak passwords used that may have unwanted consequences.

Guiding users to have a strong password with the help of password strength meters, besides being an easy process, will help improving the security of the whole & show that the website pays attention to it.